Studies of early and borderline hypertension suggest that excessive sympathetic nervous system activity may sometimes be implicated in the development of hypertension. Research in our laboratory has shown that during exposure to a reaction time task where threat of shock is used to encourage active coping, healthy young men show large temporary increases in systolic blood pressure, cardiac rate and performance mediated by sympathetic (beta-adrenergic) mechanisms. Parents of subjects with above-average heart rates during this task report a significantly greater incidence of hypertension than parents of subjects with lower heart rates. The intent of this research is to provide further evidence that high heart rate responses by young adults during active coping tasks indicate excessive sympathetic response and may indicate high risk incentive, is as effective as shock in enhancing sympathetically-mediated increases in blood pressure and cardiac performance; high heart reactivity to competition also is associated with elevated plasma renin activity and with as suppressed hostility or Type A (coronary-prone) behavior pattern. Other studies in progress examine: 1) Whether other factors affecting coping efforts (task difficulty, evaluation by others) alter cardiovascular responses to behavioral tasks; 2) whether high heart rate reactivity in the laboratory is associated with high reactivity to real-life stresses (e.g. course examinations); 3) whether active coping tasks also evoke changes in kidney function (antidiuresis, antinatriuresis) after volume-loading in humans.